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The federal government will take over TV and radio on Wednesday for a 30-second test of a system designed to inform the nation of major emergencies.

The test, initially scheduled to last for three-and-a-half minutes, will interrupt television, radio and satellite radio shows at 2 p.m. EDT. State and local tests have taken place for years, but this will be the first nationwide, comprehensive test of the National Emergency Alert System.

The system was designed to be activated on the president's orders in the event of a national emergency.

FEMA is conducting the test jointly with the Department of Homeland Security, the Federal Communications Commission and the National Oceanic and Atmospheric Administration.

"The test is being conducted as part of their ongoing efforts to keep the nation safe during emergencies and strengthen our resilience against all hazards," FEMA said in a press release.

The test's duration was shortened amid concerns such a long alert could cause panic.

"We're asking everyone to join us by spreading the word to your neighbors, co-workers, friends and family... please remember: don't stress; it's only a test," FEMA said in a blog post.

The test is part of the Emergency Alert System designed to transmit, via TV and radio, emergency alerts and warnings regarding weather threats, child abductions and other types of emergencies, according to officials.

While state and local tests already take place frequently, a simultaneous, nationwide test of the national EAS "emergency action notification" code has never occurred.